(1) Field of the Invention
The present invention relates to a poly(2-methyl phenylene oxide) homopolymer prepared from o-cresol which is biodegradable. In particular, the present invention relates to a homopolymer which has good blending properties with hydrophobic polymers. In soil experiments, the homopolymer degraded readily.
(2) Description of Related Art
Because landfill approaches to solid-waste disposal are both inefficient and increasingly expensive, traditional approaches to plastic utilization need to be replaced with better strategies. Although increased plastics recycling will occur in the future, it is likely that logistics and economics will limit the kinds and amount of plastics to be recycled and that disposal of plastics, particularly those used for packaging of food and household wastes, will continue at high volumes. Current plastic packaging materials are sophisticated blends, laminates, or mixtures that have specific mechanical, barrier, and processing properties for their applications.
There currently are three mechanisms of polymer degradation by environmental causes: photodegradable, chemically degradable, and biodegradable. There are three categories of biodegradable polymers: immiscible blends of a biodegradable polymer such as starch in a thermoplastic polymer; single-phase systems of hydrolyzable homopolymers and copolymers, and soluble polymers that can dissolve in water and presumably might then be attacked by microorganisms. To date, most single-phase biodegradable polymers have hydrolyzable linkages, including ester and amide types (S. J. Huang, in Encyclopedia of Polymer Science and Engineering, H. F. Mark et al., Eds., Wiley-Interscience, New York, Vol. 2, pp. 220-242 (1985)). Because of their polarity, these polymers do not blend well with the more hydrophobic polymers such as polystyrene and polypropylene typically used in packaging applications.
Development of hydrophobic polymers that can be biodegraded can lead to alternative systems and strategies for packaging materials. The polyphenylene ether family of polymers are miscible with other polymers, particularly those containing aromatic rings. The aromatic component of these polymers leads to their wetting of other synthetic polymers in laminate applications or miscible blends in other applications.
The problem is to develop compatible, highly biodegradable polymers which have a high molecular weight range. To date polymers based upon o-cresol have a molecular weight distribution of about 1000 up to 100,000, which is too narrow.
U.S. Pat. No. 3,383,435 to Cizek describes a blend of styrene resin and a polyphenylene ether. U.S. Pat. No. 3,306,875 to Hay et al describes the preparation of polyphenylene ethers using tertiary amine metal complexes as catalysts. These polymers have the narrow molecular weight distribution.